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Highly pathogenic avian influenza (HPAI) viruses are Category C NIAID priority pathogens and a global biodefense threat. Vaccines that provide protection against HPAI viruses are required for biodefense and pandemic preparedness. During the past decade, the H5N1 HPAI viruses have diversified genetically and antigenically leading to the need for multiple H5N1 vaccines. Although H5N1 clade 1 vaccines have been prepared, it is unlikely that they will protect against other H5N1 clades. In addition, preparation of vaccines for each potential threat virus is expensive, economically not feasible and can raise serious biosafety and biosecurity concerns. Recombinant virus-like particles (VLPs) represent a promising strategy for prevention of HPAI. VLPs have advantages in safety, efficacy, and manufacturing because they circumvent problems like slow virus growth, unpredictable yields, and host-adaptive mutations. It has been shown that VLPs induce broader immunity against divergent strains than standard influenza vaccines, especially if administered mucosally (Bright et al., 2007; Perrone et al., 2009). Furthermore, we have recently prepared multi-subtype VLP, in which several distinct subtypes of hemagglutinin (HA) were co-localized within the same VLP structure thus providing protection against multiple challenge viruses (Pushko et al., 2011; Tretyakova et al., 2013). The multi-subtype vaccines have advantage of inducing broad-range, yet traditional virus-neutralizing immune responses directed against several influenza subtypes. Here we propose the use of multi-HA VLP platform for the development of multi-H5 VLPs as a unique multi-clade H5N1 VLP vaccine. The multi-H5 VLPs will be rationally designed to co-localize within the VLP the three H5 proteins derived from three distinct H5N1 clades. The resulting triple-H5 VLPs are expected to elicit effective protection against multiple H5N1 HPAI viruses resulting in a safe and effective, broadly protective H5N1 vaccine. Particularly, we propose preparation of VLPs that co-localize H5 proteins derived from Clade 1, Clade 2.2.1.1, and Clade 2.3.2.1 viruses, all recommended by the WHO for H5N1 vaccine development. Multi-H5 VLPs will be prepared by using recombinant baculovirus expression, and genetic stability, biochemical, structural, and antigenic characteristics of VLPs will be evaluated (Sp. Aim 1). Immunogenicity and efficacy of triple-H5 VLPs will be evaluated in experimental ferret challenge model in collaboration with the Centers for Disease Control and Prevention (CDC). Both the homologous (Sp. Aim 2) and heterologous (Sp. Aim 3) H5N1 HPAI challenges are proposed in order to evaluate this novel broad-spectrum H5N1 vaccine. Young and aged ferrets will be included into the challenge studies to mimic the most vulnerable human populations. The effects of intramuscular and intranasal routes of vaccination on immune responses will be evaluated. Mechanisms of broad immunity will be elucidated including humoral, cell-mediated, and mucosal immunity. Process development and technology transfer into manufacturing environment will be carried out. Following completion of preclinical trials and process development activities, a pre-IND meeting with FDA will be planned. If successful, this novel technology may represent an innovative platform for rapid and cost-effective preparation of multivalent influenza vaccines for biodefense and pandemic preparedness.

Public Health Relevance

H5N1 influenza viruses represent a biodefense and pandemic threat to the U.S. and world population. Preparation of vaccines capable of protecting against multiple, highly pathogenic H5N1 viruses fits the mission of the National Institutes of Health (NIH) and is important for public health and pandemic preparedness. The focus of this application is the development of a conceptually new, multi-H5 influenza VLP vaccine that protects against multiple H5N1 pandemic influenza viruses. Safety and efficacy of multi-H5 VLP vaccine will be tested in ferrets following homologous and heterologous H5N1 virus challenges in collaboration between Medigen and the Centers for Disease Control and Prevention (CDC). Multi-H5 VLPs may represent a major improvement in broadly protective vaccines against H5N1 influenza viruses.